Corn is an excellent energy feed, and is ideal for finishing feeder pigs because it is high in digestible carbohydrates, low in fiber, and is very tasty feed for pigs to pigs! But corn alone will not keep pigs growing and healthy. Corn must be supplemented with Pig(s) food(s) vitamins to keep pigs healthy.
Pi is the ratio of a circle's circumference to it's diameter. The resulting number is the reason there cannot be a perfect circle. It's value is approximately 3.142 which, rounded up to the nearest whole number, would be four. It would not be three, as that would be rounding down.
On one level pi is simple: It is the ratio of a circle's circumference divided by its diameter. This ratio, for any circle, is always the same - 3.14 or so. You can prove this to yourself with a circle, a piece of tape and a ruler.